Various forms of metering devices previously have been designed including some specifically adapted for use as means to variably meter the flow of fuel to a fuel and air mixture charge forming area. Examples of previous structures of this type including features at least somewhat similar to those used in this invention are disclosed in U.S. Pat. Nos. 213,186, 2,321,211, 2,447,264, 2,823,021, 2,960,996, 3,207,490 and 3,233,878. However, these previously patented devices are not capable of precise fluid flow control by the use of only simple basic structural elements.